Auxiliary covering



. phonated castor oil Patented Aug. 18, 1942 UNITED STATES' PATENT Omar I m .ifi'iifmm Willard 0. Manor, Monroe, Mich, acsignor to Consolidated Paper Company, Monroe, Mich, a

corporation of Michigan No Drawing. Application January 8, 1940,

' Serial No. 312,907

20mm. (ctzos-si) or This invention relates to protective coating. This invention has utility in isolating contained material from the container, especially after congeallng, as well as isolating the material of the container from the contents even as hot charged thereinto in molten or liquid form. Peculiar advantages, such as reinforcement and flexibility to withstand scoring after coating is applied, have arisen in the use of an overcoat of the auxiliary protective covering in conjunction with the primary coating or covering composition. This process and composition asherein rendered effective fiber board, paper board, box board and the like, and the substances handled have been asphalt, pitch, tar, resins, and the general classes of like substances, even to the realm of greases and more or less thick pastes, a degree of hardness, but which in many instances involve sticky characteristics and in which di'fflculties arise in isolating the contents from the container, whether by opening to pour or slide out, or by ripping or peeling the container therefrom.

While this case is more directly to the auxiliary covering of the laminated coating, it has been effective in extending the range for practical use of special coatings. For instance, a granular coating herein termed has involved a general filler of preferably fine or impalpable clay or kaolin, say 40 parts; sulup to '7 parts; sodium nitrate, 1 part; glue, 2 parts; ammonium carbonate, 2 /2 parts; karaya gum, 1 part; and approximately the reverse order of mixing to that herein stated, with the water to an extent to give a consistency of house paint. This primary granu lar coating may be applied to the sheet stock by a predetermined desired method chosen to meet the, then existing conditions, whether by spraying, brushing, rolling, or even dipping. A manner found desirable to apply the coating in two directions, say at right angles, resulting in a thin, and continuous coating. Such uniform layer is weakly adherent and is an effective dam for asphalt and the like as this coatin used for the lining of containers. In carrying out this invention, this overcoat or auxiliary coating composition is primarily what might be termed a starch paste, whether such be in the carbohydrate series of cassava, corn, or potato. Such as a hot mix may be in the range of 100 pounds of this starch paste, of which 5 to 55 1 has. been in conjunction with which may or may not get to for coating box board stock is evenly dispersed,

composition is 18 per cent is starch and 82 to 95 per cent is water. Against fracture hazard there may be included in such paste of 100 pounds, say pounds of glycerine. On occasion up to 2 per cent caustic soda may be used when the starch be not laundry starch but corn or potato starch.

' Fluidity, for greater proportion of starch to enter the paste and thereby to be carried into themixture, is promoted by the presence of a wettingout agent such as asulphonated oil or a soap up to 2 or 3 per cent.

Furthermore, in practice, as to the reverse or outer side of the sheet stock for the container in having such given a waterproof coating which may be of paraflin or other waxes, rosin mixtures, or the like.

Commercial products have been adopted as eflicient in this overcoat of hot mix starch. However, cold mix may be adopted on the basis of 16 parts of starch, 24 parts of water, to which is added a caustic soda, 36 Baum, 4 parts as against 32 parts of water, the alkali promoting the reprimary" which may be i applied to fiber board, box board and the like,

action as cold. Neutralizing may then occur by 3.1 parts of commercial hydrochloric acid in' 20 I parts of water. To this may be added 8 parts of glycerine, all by weight. In the event there is desirability for further toughening this film as a seeming skin or plastic coating, there may be incorporated therewith part formaldehyde with /2 part of water, the composition then to be mixed some fifteen minutes.

Instead of adopting in the cold mix the foregoing parts ratio, there may be taken 2 /2 parts of starch, 15 partsof water, and 2 /2 parts of caustic soda by weight; this mix being neutralized with hydrochloric acid. With such'as the paste body, mixing thereof may occur with water up to 25 per cent andIwith glycerine of as much as l per cent. In the use of commercial material herein, this cold mixed latter material -may form a jelly mass and then be mixed to the consistency of thin paint for application to .sheet material and upon the primary coating. This carbohydrate base or starch paste is of such toughness or resiliency in responding to normal handling that it holds the stock against fracture of the coatings therefrom and thus permits shipping of the coated stock before or after blanking and before or after scoring.

It is to be noted that the general characteristic of this carbohydrate or starch paste is for normal adherence to the fiber board, box board or the like. The relatively inert body of the primary coating takes up this adherence and is a step may be taken to isolate not only this adherent material but the contents from the container wall. It thus serves as a supplemental coating or reinforcement for the primary inert body-carrying coa 'l 'lig starch film is eilective as a barrier to penetration of molten materials up to the time the temperature or such materials would be high enough to decompose the starch. From that point and at higher temperatures the decomposed parts, including the carbon, ar dispersed in the voids or the primarycoating, thereby not only continuing the damming action but supplementing that of the more or less porous primary clay coating. In the handling of the high temperature molten materials, the starch or secondary coating alone would be ineffective. By ineffective coating as herein mentioned, it is conceded the starch coating or film alone would be ineffective as a dam against adherence or penetration as to some contents, especially under high temperature conditions. Accordingly, the starch paste is effective in its response say as broken down by. the heat to the-end that its body or carbon as so attacked may fill in the pores of the inert filler and serve as an improved dam with the inert filler, while this paste of itself might be ineffective as such a dam. Tlie inert filler is, as herein, a silicious material as bentonite, kaolin, or clay, which in the normal handling of the contents is spread as a thin film, held as such film to provide a dam. Therefore, when the contents contact and cover this laminated coating and congeal, there is no penetration of the dam by the contents against, into, or through the container walls.

It appears that the higher the percentage of solids in the film or secondary coating, the more effective such becomes, especially in score protection of the coated sheet material. Furthermore, it being desirable to score the sheet material after coating, increase in film toughness is also desirable. Both these latter qualities have been increased by adding a gum to the ingredients of the secondary coating. The gum may be chosen from a wide Variety or plant gums but -for commercial effectiveness and economy dextrin has proven satisfactory. As used, a typical formula for the secondary coating may be approximately 6 pounds of starch, 10 pounds of dextrin, 30 pounds of glycerine, 104 pounds of water, with considerable variation in these amounts to meet various conditions under which said coating is to be applied, such as humidity, temperature, and method of application. The water may be increased or the starch decreased to eilect the viscosity, while the glycerine may also be varied and the dextrin adding materially to the solid contents as required without a proportionate increase in the workable spreadability.

The approximate percentages of thes latter into sticking between the container and the container contents, a coating composition of sealing body normally adherent to the container but isolated from the container sheet material by and forming a jacket on said separable coating composition wherein the separable coating is inert with respect to the contents, and where the nor-' mally adherent coating is of flexible nature.

2. The combination for sheet stock covering material of a base coating composition of dam providing body relatively weakly adherent and an overcoating sealing body composition normally strongly adherent to the sheet material and coacting to form a jacket on and isolated from the sheet material by the base coating composition wherein the weakly adherent coating is inert with respect to the contents, and where the strongly adherent coating is of flexible nature.

3. In a fibrous container for packaging materials normally adherent thereto, a coating comprising a primary granular coating having an inert filler such as kaolin, and a secondary coating forming a film thereover including starch.

4. In a fibrous container for packaging materials normally adherent thereto, a coating comprising a primary granular coating having an inert filler such as kaolin, a secondary coating forming a film "thereover including starch, and a gum serving as a film toughening agent.

5. In a fibrous container for packaging materials normally adherent thereto, a coating comprising a primary granular coating having aninert filler such as kaolin, a secondary coating forming a film thereover-including starch, and dextrin serving as a film toughening agent.

6. In a fibrous container for packaging materials normally adherent thereto, a coating comprising a primary granular coating having an inert filler such as kaolin, and a secondary coating forming a film thereover including starch, glycerine and water in such proportions as to be of a spreadable viscosity.

7. A container, such as of fiber board, for a hot substance, such as asphalt, a granular coating composition thereon of inert body of the character of kaolin providing a primary base coating composition, and which primary coating has a film coating composition thereon of the character of starch paste forming a sealing body holding the base in position.

WILLARD O. MANOR. 

